1. Field of the Invention
The present invention relates to a mixing element of a static mixer fixed in a cylindrical casing and including right-handed spiral blades and left-handed spiral blades, which respectively have a shape twisted approximately 180 degrees, and are alternately and continuously provided in an axial direction so as to make end parts of the adjacent spiral blades to cross almost orthogonally.
2. Description of the Conventional Art
When two or more kinds of fluid are mixed, a static mixer not having a driving part has been conventionally widely used. For example, U.S. Pat. No. 3,953,002, and U.S. Pat. No. 4,408,893 disclose such a static mixer including a cylindrical casing and a mixing element fixed in the casing, where the mixing element includes right-handed spiral blades and left-handed spiral blades, which respectively have a shape twisted approximately 180 degrees, and are alternately and continuously provided in an axial direction so as to make end parts of the adjacent spiral blades to cross almost orthogonally.
As for the static mixer, when two or more kinds of fluids flow continuously into a cylindrical casing, in which a mixing element is fixed, from one side of the casing, two or more kinds of the continuously flowing-in fluids flow toward the other side of the casing in a space formed with an inner peripheral face of the casing and two or more spiral blades of the mixing element. During this process, the fluids are continuously stirred and mixed by operations of dividing, converting, and reversing by two or more spiral blades of the mixing element and a mixture of two or more kinds of the fluids is discharged from the other side of the casing. Further, in the static mixer, by changing the number or diameter of a spiral blade of a mixing element, the mixer can be used for mixing of various kinds of fluids, e.g., mixing of fluids having low viscosity or mixing of fluids having high viscosity.
In the static mixer, since two or more kinds of fluids flow into a casing, in which a mixing element is fixed, continuously from one side of the casing, these fluids can be mixed without using a means such as a driving part. However, two or more kinds of fluids finally remain unmixed in a space formed with an inner peripheral face of the casing and two or more spiral blades of the mixing element, and thus there is a fault that the remaining fluids become wastes. More particularly, when two or more kinds of the fluids are, for example, a high cost material constituting a dental adhesive, there is a fault that the economic loss is remarkably high.
Then, in order reduce the residual amount of two or more kinds of unmixed fluids in the static mixer, Japanese Patent No. 2890314 discloses a mixing element including main faces which are spirally and symmetrically twisted around a longitudinal axis and opposes to each other. The main faces have such structure that a cross section of a baffle which vertically cross with the above-mentioned axis has a recess shape, and extend along the longitudinal axis from a first end part to a second end part of the baffle.
When the baffle is provided in a tubular housing, the recessed faces of the main faces can demarcate one pair of paths, which has an approximately egg shape or ellipse shape and does not have an acute angle part, with the housing on each side of the baffle.
This mixing element has recessed faces extending along the axial direction from a first end part to a second end part of a baffle (that is, a spiral blade), and one pair of paths having an approximately egg shape or ellipse shape without having an acute angle part are demarcated on each side of the spiral blade. Thus, even when each side of the spiral blade has an a cuter angle, that is, even when the length in the axial direction of the spiral blade is slightly shortened than that of a conventional mixing element, this mixing element can obtain similar mixing efficiency to that of the conventional mixing element. However, there is a fault that mixing efficiency for each spiral blade hardly differs from mixing efficiency of a spiral blade of a conventional mixing element, so that this mixing element needs the same number of spiral blades as those of the conventional mixing element. Thus, since the length in the axial direction cannot be remarkably shortened than that of the conventional mixing element, there is a fault that the residual amount of two or more kinds of unmixed fluids cannot be reduced as much as possible.